为什么静态索引在C＃中不允许？我不明白为什么他们不应该被允许的，而且他们可能是非常有用的。

Why are static indexers disallowed in C#? I see no reason why they should not be allowed and furthermore they could be very useful.

例如：

static class ConfigurationManager {

        public object this[string name]{
            get{
                return ConfigurationManager.getProperty(name);
            }
            set {
                ConfigurationManager.editProperty(name, value);
            }
        }

        /// <summary>
        /// This will write the value to the property. Will overwrite if the property is already there
        /// </summary>
        /// <param name="name">Name of the property</param>
        /// <param name="value">Value to be wrote (calls ToString)</param>
        public static void editProperty(string name, object value) {
            DataSet ds = new DataSet();
            FileStream configFile = new FileStream("./config.xml", FileMode.OpenOrCreate);
            ds.ReadXml(configFile);

            if (ds.Tables["config"] == null) {
                ds.Tables.Add("config");
            }

            DataTable config = ds.Tables["config"];

            if (config.Rows[0] == null) {
                config.Rows.Add(config.NewRow());
            }

            if (config.Columns[name] == null) {
                config.Columns.Add(name);
            }

            config.Rows[0][name] = value.ToString();

            ds.WriteXml(configFile);
            configFile.Close();
        }

        public static void addProperty(string name, object value) {
            ConfigurationManager.editProperty(name, value);
        }

        public static object getProperty(string name) {
            DataSet ds = new DataSet();
            FileStream configFile = new FileStream("./config.xml", FileMode.OpenOrCreate);
            ds.ReadXml(configFile);
            configFile.Close();


            if (ds.Tables["config"] == null) {
                return null;
            }

            DataTable config = ds.Tables["config"];

            if (config.Rows[0] == null) {
                return null;
            }

            if (config.Columns[name] == null) {
                return null;
            }

            return config.Rows[0][name];
        }
    }

以上code将极大地从一个静态的索引中获益。然而，它不能编译，因为静态的索引是不允许的。为什么会这样？

The above code would benefit greatly from a static indexer. However it won't compile because static indexers are not allowed. Why is this so?

推荐答案

索引符号要求引用这。由于静态方法不具有参考类的特定实例，你不能使用这和他们在一起，因此不能在静态使用索引符号的方法。

Indexer notation requires a reference to this. Since static methods don't have an reference to a particular instance of the class, you can't use this with them, and consequently you can't use indexer notation on static methods.

该问题的解决方案是使用Singleton模式如下：

The solution to your problem is using a singleton pattern as follows:

    public class Utilities
    {
        static ConfigurationManager _configurationManager = new ConfigurationManager();
        public static ConfigurationManager ConfigurationManager
        {
            get
            {
                return _configurationManager;
            }
        }
    }

    public class ConfigurationManager
    {
        public object this[string value]
        {
            get
            {
                return new object();
            }
            set
            {
                // set something
            }
        }
    }

现在你可以叫 Utilities.ConfigurationManager [someKey] 使用索引符号。

Now you can call Utilities.ConfigurationManager["someKey"] using indexer notation.